Microscopic and Spectroscopic Analyses of Chlorhexidine Tolerance in Delftia acidovorans Biofilms

Rema, Tara; Lawrence, John R.; Dynes, James J.; Hitchcock, Adam P.; Korber, Darren R.

doi:10.1128/aac.02984-14

Cited by 21 publications

(21 citation statements)

References 62 publications

(88 reference statements)

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“…40 The additional band characteristics of chlorhexidine appear at 1,492 cm -1 , which is related to the chlorophenol groups of chlorhexidine. 41 The spectrum of PVA/chitosan/AgNPs/PEO/chlorhexidine ( Figure 5F) shows the characteristic absorption bands for pure PVA, pure chitosan, and the additional absorption bands characteristic of PEO and of chlorhexidine. The additional band of PEO appears at 1,644 cm -1 , which is attributed to the C=O stretching vibration.…”

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confidence: 99%

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Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

Hassiba

Zowalaty

Webster

et al. 2017

IJN

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confidence: 99%

“…42 The additional band characteristic of chlorhexidine appears at 1,492 cm -1 , which is related to the chlorophenol groups of chlorhexidine. 41 …”

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confidence: 99%

Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

Hassiba

Zowalaty

Webster

et al. 2017

IJN

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“…e read with great interest the recently published work of Rema and colleagues (1). In that work, the authors verify the role of chlorhexidine (CHX) within the structure of Delftia acidovorans biofilm in two strains: one wild strain, tolerant to CHX, and a mutant with a Tn5 mutation.…”

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confidence: 86%

“…On the other hand, antimicrobial agents with zwitterionic, neutral, or negatively charged species may preserve their activities against D. acidovorans isolates (5). Considering both the data found by Rema et al (1) and the information about the characteristics of outer membrane proteins of D. acidovorans, we may suppose that CHX actually acts only at the intercellular level, disrupting the biofilm but not killing the cells, suggesting the need for multiple approaches in order to reach an effective clearance of D. acidovorans biofilms.…”

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Insight into the Role of Chlorhexidine in Delftia acidovorans Biofilm Formation

Camargo¹,

Bruder‐Nascimento²

2015

Antimicrob Agents Chemother

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b W e read with great interest the recently published work of Rema and colleagues (1). In that work, the authors verify the role of chlorhexidine (CHX) within the structure of Delftia acidovorans biofilm in two strains: one wild strain, tolerant to CHX, and a mutant with a Tn5 mutation.As their main results, Rema et al. demonstrate by confocal laser scanning microscopy (CLSM) that a subinhibitory concentration of chlorhexidine (CHX) (10 g/ml) increased the biofilm thickness of the wild strain WT15 (MIC ϭ 15 g/ml) and that "the proportion of viable cells increased with the distance from the attachment surface," suggesting that a subinhibitory concentration of CHX stimulates biofilm production in WT15 and does not affect the cells' viability. On the other hand, the dose of 10 g/ml significantly reduced the thickness of the biofilm in the MT51 strain (MIC ϭ 1.0 g/ml), but "total viable cells decreased significantly (P Ͻ 0.05) with depth following both 10 g/ml and 30 g/ml CHX treatment," indicating a possible impact on the intercellular arrangement of MT51 biofilms but not on isolated cells. That is, exposure to CHX did not influence cell viability, even at inhibitory doses, as was also observed for WT15 with subinhibitory CHX dosages, which is different from what was reported in the discussion: "MT51 cells in direct contact with CHX were affected by the biocide to a greater extent than were the cells located deep within the biofilm matrix."With their scanning transmission X-ray microscopy (STXM) results, the authors verify that CHX at subinhibitory levels increased the protein amount in some regions of WT15 biofilms and also state that this phenomenon may be explained by the presence of two distinguishable patterns in WT15 biofilms (as in biofilms not treated with CHX). In MT51 strains, however, CHX did not affect the biofilm protein composition. Taken together, these findings may indicate the absence of a role for CHX in affecting biofilm protein proportions.In addition, infrared spectroscopy (IR) demonstrated that a prominent peak at 1,492 cm Ϫ1 might explain the higher levels of accumulation of CHX in MT51 biofilm strains and not a disruption of cells.Taking all those findings together, the authors attributed to the paradigm that biofilm growth renders cells more resistant than planktonic counterparts and conclude that "Delftia acidovorans biofilms provided an ideal model system for integrating analysis of CLSM, STXM, and IR data to gain insights into bacterial interactions with CHX at the micro-to nanoscales of resolution."In their concluding remarks, indeed, the authors speculate about a potential role of the cell membrane in CHX resistance. In our view, it seems that the authors neglected to consider a particular feature of the D. acidovorans cell membrane that can contribute to its resistance or tolerance to CHX. The major protein compounds of the outer membrane of D. acidovorans are outer membrane protein 32 (Omp32) (2) and two less prominent proteins, Omp37 and Omp21 (3). Previous characterization of Omp32...

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“…Hyperspectral chemical imaging combined with confocal microscopy is an up-and-coming research field with great potential for the discovery of new insights about biofilm formation encompassing spatially resolved spectral data obtained through a variety of modalities (e.g., Raman microscopy [ 75 – 78 ] and FTIR microscopy [ 79 – 81 ] chemical imaging). It goes beyond the capabilities of conventional imaging and spectroscopy by obtaining spatially resolved spectra from objects at spatial resolutions down to the level of a single cell ( 82 ).…”

Section: Biofilm Imagingmentioning

confidence: 99%

Optical Sensing of Microbial Life on Surfaces

Fischer

Triggs

Krauss

2016

Appl Environ Microbiol

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The label-free detection of microbial cells attached to a surface is an active field of research. The field is driven by the need to understand and control the growth of biofilms in a number of applications, including basic research in natural environments, industrial facilities, and clinical devices, to name a few. Despite significant progress in the ability to monitor the growth of biofilms and related living cells, the sensitivity and selectivity of such sensors are still a challenge. We believe that among the many different technologies available for monitoring biofilm growth, optical techniques are the most promising, as they afford direct imaging and offer high sensitivity and specificity. Furthermore, as each technique offers different insights into the biofilm growth mechanism, our analysis allows us to provide an overview of the biological processes at play. In addition, we use a set of key parameters to compare state-of-the-art techniques in the field, including a critical assessment of each method, to identify the most promising types of sensors. We highlight the challenges that need to be overcome to improve the characteristics of current biofilm sensor technologies and indicate where further developments are required. In addition, we provide guidelines for selecting a suitable sensor for detecting microbial cells on a surface.

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Microscopic and Spectroscopic Analyses of Chlorhexidine Tolerance in Delftia acidovorans Biofilms

Cited by 21 publications

References 62 publications

Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

Insight into the Role of Chlorhexidine in Delftia acidovorans Biofilm Formation

Optical Sensing of Microbial Life on Surfaces

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